20 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



of the same line in the spectrum of a Geissler tube held be- 

 fore the telescope has promised great results, and in the 

 hands of Huggins and Vogel has yielded apparently relia- 

 ble information. Secchi took up the problem in 1863, but 

 without reaching satisfactory results, and attributed his 

 negative conclusions at that time to the great difficulty and 

 delicacy of the research. It is known, too, that the theory 

 of Doppler (1842), upon which the principle of this method 

 of research depends, has been seriously questioned by Van 

 der Willigen. At Greenwich, during the past year, the ques- 

 tion has been taken up on its observational side, and the re- 

 sults reached, which are often contradictory, have been pub- 

 lished in the Monthly Notices of the Royal Astron. Society, 

 vol. xxxvi., 13. 30. 



In view of these known difficulties, the recent researches 

 of Secchi on this point are of great importance. He has pre- 

 pared a table (a portion of which is reproduced below) in 

 which the results of the various observers are exhibited. 

 The sign + shows that the star was moving away from the 



earth, and 



that it was approaching it. 



In his considerations upon the complete table, Secchi 

 makes the following remarks: 



1. That at Greenwich almost all the results are negative, 

 a positive result being the exception ; 2. The different days' 

 results are quite discordant ; 3. Huggins's results are nearly 

 all 4- : 4. The results of Hug^o-ms as to the motion of Coggia's 

 comet are not in accord with the known direction of this 

 comet's motion ; 5. The mean numerical results of the vari- 

 ous observers are widely different. In view of these discord- 

 ances, Secchi has made experiments upon Sirius with the ob- 

 ject of determining whether there may be a systematic source 

 of error, either in the instrument or in the manner of observ- 

 ing, which may cause the displacement of the spectral ray. 



